High abrasion resistance is among the performances of films desired in the field of coating films containing organosilicon compounds and resins as matrixes.
In particular, films are required to perform well in both abrasion resistance and other properties such as refractive index and transparency in the field of hardcoat films and primer films that protect the surface of optical substrates such as spectacle lenses.
A known approach to improving the refractive index and the abrasion resistance of such films is to add metal oxide particles to film-forming coatings.
For example, JP-A-H05-002102 describes hardcoat films that are composed of a matrix and composite oxide particles including an iron oxide component and a titanium oxide component. According to the disclosure, such films exhibit high refractive index, transparency and abrasion resistance.
However, composite oxide particles show low reactivity with respect to a matrix component. This problem is addressed by treating the surface of the particles with a silane-coupling agent to enhance the reactivity with respect to matrixes.
For example, JP-A-H07-076671 describes a coating composition for optical plastic shaped articles containing titanium oxide composite fine particles whose surface has been modified with a silane-coupling agent.
However, there has been a demand for a further improvement of these surface modification treatment methods in order to enhance film performance.
Patent Literature 1: JP-A-H05-002102
Patent Literature 2: JP-A-H07-076671
The present invention aims to solve the conventional problems mentioned above. It is therefore an object of the invention to provide surface-treated fine particles which have excellent reactivity with respect to a matrix component and allow films to exhibit excellent coating performance.